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Plasma response to a cometary outburst: Rosetta Plasma Consortium observations during comet 67P/Churyumov-Gerasimenko outburst event on 19 February 2016

Abstract : Cometary outbursts are one of the most spectacular aspects of comet behavior. They are characterized by an abrupt increase in cometary brightness followed by a gradual fall off to the pre-event brightness. Although there are several studies on outburst events, to our knowledge, no detailed analysis on the variation of the cometary plasma environment during an outburst has ever been reported. On 19 February 2016, when comet 67P/Churyumov-Gerasimenko was at a heliocentric distance of 2.4 AU, an outburst event, characterized by two orders of magnitude increase in coma surface brightness, took place. Rosetta was at a distance of 30 km from the comet nucleus, orbiting with a relative speed of 0.17 m/s. The Rosetta Plasma Consortium (RPC) provided in-situ measurements of the cometary plasma, embedded in the solar wind, and the associated magnetic field during this outburst, as the dust and gas expelled from the comet were passing by the spacecraft. While the neutral density (ROSINA/COPS) at the spacecraft position increased by a factor of 1.5, the local plasma density (RPC/MIP) was found to increase by a factor of 3 during the outburst event, driving the spacecraft potential more negative (RPC/LAP). The event was characterized by the energy degradation of energetic (10s of eV) electrons (RPC/IES). In response to the outburst, the local magnetic field exhibited a slight increase in amplitude and a slow rotation (RPC/MAG). A weakening of 10-100 mHz magnetic field fluctuations was also observed during the outburst. The RPC instruments show that the effects of the outburst on the plasma lasted for about 4 hours, from 1000 UT to 1400 UT. Detailed analyses of the observations made by RPC along with ROSINA/COPS will be presented in the paper.
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https://hal-insu.archives-ouvertes.fr/insu-03573490
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Submitted on : Monday, February 14, 2022 - 5:08:19 PM
Last modification on : Tuesday, May 10, 2022 - 3:24:58 PM

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R. Hajra, T. Bruce, H. Pierre, M. F. Galand, K. L. Heritier, et al.. Plasma response to a cometary outburst: Rosetta Plasma Consortium observations during comet 67P/Churyumov-Gerasimenko outburst event on 19 February 2016. American Geophysical Union, 2016, San Francisco, United States. ⟨insu-03573490⟩

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